Fri·Nov 27, 2020Friday·November 27, 2020

1. 01*

   Impact of a thermal medium on newly observed $Z_{cs}(3985)$ resonance and its $b$-partner

   J.Y. Süngü🇹🇷 · A. Türkan🇹🇷 · H. Sundu🇹🇷 · E. Veli Veliev🇹🇷

   Motivated by the very recent discovery of the strange hidden-charm exotic state $Z_{cs}(3985)$ by the BESIII Collaboration, we study possible interpretation of this exotic state both at $T=0$ and $T\ne 0$. We analytically compute the mass and meson-current coupling constant of this resonance with spin-parity $J^{PC}=1^{+-}$ at finite temperature approximation up to sixth order of the thermal operator dimension including non-perturbative contributions. Extracting thermal mass and meson-current coupling constant sum rules, the modifications on properties of $Z_{cs}(3985)$ state in hot medium is determined. As a by product, the hadronic parameters of the bottom partner of $Z_{cs}(3985)$ is estimated as well. Moreover the search of temperature effects on the hadronic parameters of hidden-charm meson $Z_{cs}(3985)$ and the bottom partner make us understand the phase transitions, chiral symmetry breaking and the properties of hot-dense matter in QCD.

   hep-phEPJC(2022)·26 citations
2. 02*

   Dirac neutrinos and $N_{\mathrm{eff}}$ II: the freeze-in case

   Xuheng Luo🇺🇸 · Werner Rodejohann🇩🇪 · Xun-Jie Xu🇩🇪

   We discuss Dirac neutrinos whose right-handed component ${\nu }_R$ has new interactions that may lead to a measurable contribution to the effective number of relativistic neutrino species $N_{\mathrm{eff}}$. We aim at a model-independent and comprehensive study on a variety of possibilities. Processes for ${\nu }_R$-genesis from decay or scattering of thermal species, with spin-0, spin-1/2, or spin-1 initial or final states are all covered. We calculate numerically and analytically the contribution of ${\nu }_R$ to $N_{\mathrm{eff}}$ primarily in the freeze-in regime, since the freeze-out regime has been studied before. While our approximate analytical results apply only to freeze-in, our numerical calculations work for freeze-out as well, including the transition between the two regimes. Using current and future constraints on $N_{\mathrm{eff}}$, we obtain limits and sensitivities of CMB experiments on masses and couplings of the new interactions. As a by-product, we obtain the contribution of Higgs-neutrino interactions, $\Delta N_{\mathrm{eff}}^{\mathrm{SM}}\approx 7.5\times 10^{-12}$, assuming the neutrino mass is 0.1 eV and generated by the standard Higgs mechanism.

   hep-phastro-ph.COJCAP(2021)·77 citations
3. 03*

   Coulomb nuclear interference effect in dipion production in ultraperipheral heavy ion collisions

   Yoshikazu Hagiwara🇨🇳 · Cheng Zhang🇨🇳 · Jian Zhou🇨🇳 · Ya-jin Zhou🇨🇳

   We study exclusive ${\pi }^{+}{\pi }^{-}$ pair production near ${\rho }^0$ resonance peak in ultraperipheral heavy ion collisions. Pion pair can either be produced via two photon fusion process or from the decay of ${\rho }^0$ in photon-nuclear reaction. At very low pair transverse momentum, the electromagnetic and nuclear amplitudes become comparable. We show that the Coulomb nuclear interference amplitude gives rise to sizable $\cos \varphi$ and $\cos 3\varphi$ azimuthal asymmetries, which can be used to constrain the phase of the dipole-nucleus scattering amplitude.

   hep-phPRD(2021)·27 citations
4. 04*

   Dark sector production and baryogenesis from not quite black holes

   Ufuk Aydemir🇨🇳 · Jing Ren🇨🇳

   Primordial black holes have been considered as an attractive dark matter candidate, whereas some of the predictions heavily rely on the near-horizon physics that remains to be tested experimentally. As a concrete alternative, thermal 2-2-holes closely resemble black holes without event horizons. Being a probable endpoint of gravitational collapse, they not only provide a resolution to the information loss problem, but also naturally give rise to stable remnants. Previously, we have considered primordial 2-2-hole remnants as dark matter. Due to the strong constraints from a novel phenomenon associated with remnant mergers, only small remnants with close to the Planck mass can constitute all of dark matter. In this paper, we examine the scenario that the majority of dark matter consists of particles produced by the evaporation of primordial 2-2-holes, whereas the remnant contribution is secondary. The products with light enough mass may contribute to the number of relativistic degrees of freedom in the early universe, which we also calculate. Moreover, 2-2-hole evaporation can produce particles that are responsible for the baryon asymmetry. We find that baryogenesis through direct B-violating decays or through leptogenesis can both be realized. Overall, the viable parameter space for the Planck remnant case is similar to primordial black holes with Planck remnants. Heavier remnants, on the other hand, lead to different predictions, and the viable parameter space remains large even when the remnant abundance is small.

   hep-phastro-ph.COgr-qcCPC(2021)·6 citations
5. 05*

   A natural mechanism for approximate Higgs alignment in the 2HDM

   Patrick Draper🇺🇸 · Andreas Ekstedt🇨🇿 · Howard E. Haber🇺🇸

   The 2HDM possesses a neutral scalar interaction eigenstate whose tree-level properties coincide with the Standard Model (SM) Higgs boson. In light of the LHC Higgs data which suggests that the observed Higgs boson is SM-like, it follows that the mixing of the SM Higgs interaction eigenstate with the other neutral scalar interaction eigenstates of the 2HDM should be suppressed, corresponding to the so-called Higgs alignment limit. The exact Higgs alignment limit can arise naturally due to a global symmetry of the scalar potential. If this symmetry is softly broken, then the Higgs alignment limit becomes approximate (although still potentially consistent with the current LHC Higgs data). In this paper, we obtain the approximate Higgs alignment suggested by the LHC Higgs data as a consequence of a softly broken global symmetry of the Higgs Lagrangian. However, this can only be accomplished if the Yukawa sector of the theory is extended. We propose an extended 2HDM with vector-like top quark partners, where explicit mass terms in the top sector provide the source of the soft symmetry breaking of a generalized CP symmetry. In this way, we can realize approximate Higgs alignment without a significant fine-tuning of the model parameters. We then explore the implications of the current LHC bounds on vector-like top quark partners for the success of our proposed scenario.

   hep-phJHEP(2021)·21 citations
6. 06*

   Cancellation in Dark Matter-Nucleon Interactions: the Role of Non-Standard-Model-like Yukawa Couplings

   Debottam Das (Bhubaneswar, Inst. Phys. and HBNI, Mumbai)🇮🇳 · Bibhabasu De (Bhubaneswar, Inst. Phys. and HBNI, Mumbai)🇮🇳 · Subhadip Mitra (Hyderabad, IIIT)🇮🇳

   Extensive searches to probe the particle nature of dark matter (DM) have been going on for some decades now but, so far, no conclusive evidence has been found. Among various options, the Weakly Interacting Massive Particles (WIMP) remains one of the prime possibilities as candidates for DM near the TeV scale. Taking a phenomenological view, such null results may be explained for a generic WIMP in a Higgs-portal scenario if we allow the light-quark Yukawa couplings to assume non-Standard Model (non-SM)-like values. This follows from a cancellation among different terms in the DM-nucleon scattering which can, in turn, lead to a vanishingly small direct-detection cross section. It might also lead to isospin violation in the DM-nucleon scattering. Such non-SM values of light-quark Yukawa couplings may be probed in the high luminosity run of the LHC.

   hep-phPLB(2021)·20 citations
7. 07*

   Analysis of the possible $D{\bar{D}}_{s0}^{\ast }(2317)$ and $D^{\ast }{\bar{D}}_{s1}^{\ast }(2460)$ molecules with QCD sum rules

   Zun-Yan Di🇨🇳 · Zhi-Gang Wang🇨🇳 · Guo-Liang Yu🇨🇳

   In this article, we assume that there exist the pseudoscalar $D{\bar{D}}_{s0}^{\ast }(2317)$ and $D^{\ast }{\bar{D}}_{s1}^{\ast }(2460)$ molecular states $Z_{1,2}$ and construct the color singlet-singlet molecule-type interpolating currents to study their masses with the QCD sum rules. In calculations, we consider the contributions of the vacuum condensates up to dimension-10 and use the formula $\mu =\sqrt{M_{X/Y/Z}^2-{\left(2{\mathbb{M}}_c\right)}^2}$ to determine the energy scales of the QCD spectral densities. The numerical results, $M_{Z_1}=4.61_{-0.08}^{+0.11}\text{GeV}$ and $M_{Z_2}=4.60_{-0.06}^{+0.07}\text{GeV}$, which lie above the $D{\bar{D}}_{s0}^{\ast }(2317)$ and $D^{\ast }{\bar{D}}_{s1}^{\ast }(2460)$ thresholds respectively, indicate that the $D{\bar{D}}_{s0}^{\ast }(2317)$ and $D^{\ast }{\bar{D}}_{s1}^{\ast }(2460)$ are difficult to form bound state molecular states, the $Z_{1,2}$ are probably resonance states.

   hep-phCommun.Theor.Phys.(2019)·11 citations
8. 08*

   Analytical representation for amplitudes and differential cross section of pp elastic scattering at 13 TeV

   E. Ferreira🇧🇷 · A. K. Kohara🇧🇷 · T. Kodama🇧🇷

   With analytical representation for the pp scattering amplitudes introduced and tested at lower energies, a description of high precision is given of the $d\sigma /dt$ data at $\sqrt{s}$= 13 TeV for all values of the momentum transfer, with explicit identification of the real and imaginary parts. In both $t$ and $b$ coordinates the amplitudes have terms identified as of non-perturbative and perturbative nature, with distinction of their influences in forward and large $|t|$ ranges and in central and peripheral regions respectively. In the forward range, the role of the Coulomb-nuclear interference phase is investigated. The energy dependence of the parameters of the amplitudes are reviewed and updated, revealing a possible emergence of a peculiar behavior of elastic and inelastic profiles in b-space for central collisions, which seems to be enhanced quickly at higher energies. Some other models are also briefly discussed in comparison, including the above mentioned behavior in b-space.

   hep-phEPJC(2021)·9 citations
9. 09*

   Massive kite diagrams with elliptics

   M.A. Bezuglov🇷🇺 · A.I. Onishchenko🇷🇺 · O.L. Veretin🇩🇪

   We present the results for two-loop massive kite master integrals with elliptics in terms of iterated integrals with algebraic kernels. The key ingredients are new integral representations for sunset subgraphs in $d=4-2ϵ$ and $d=2-2ϵ$ dimensions together with differential equations for considered kite master integrals in $A+Bϵ$ form. The obtained results can be easily generalized to all orders in $ϵ$-expansion and show that the class of functions defined as iterated integrals with algebraic kernels may be large enough for writing down results for a large class of massive Feynman diagrams.

   hep-phhep-thNPB(2021)·20 citations
10. 10*

    Describing the Migdal effect with a bremsstrahlung-like process and many-body effects

    Zheng-Liang Liang🇨🇳 · Chongjie Mo🇨🇳 · Fawei Zheng🇨🇳 · Ping Zhang🇨🇳

    Recent theoretical studies have suggested that the suddenly recoiled atom struck by dark matter (DM) particle is much more likely to excite or lose its electrons than expected. Such Migdal effect provides a new avenue for exploring the sub-GeV DM particles. There have been various attempts to describe the Migdal effect in liquids and semiconductor targets. In this paper we incorporate the treatment of the bremsstrahlung process and the electronic many-body effects to give a full description of the Migdal effect in bulk semiconductor targets diamond and silicon. Compared with the results obtained with the atom-centered localized Wannier functions (WFs) under the framework of the tight-binding (TB) approximation, the method proposed in this study yields much larger event rates in the low energy regime, due to a ${\omega }^{-4}$ scaling. We also find that the effect of the bremsstrahlung photon mediating the Coulomb interaction between recoiled ion and the electron-hole pair is equivalent to that of the exchange of a single phonon.

    hep-phcond-mat.mtrl-sciPRD(2021)·43 citations
11. 11*

    Two-Neutrino Double Beta Decay with Sterile Neutrinos

    Patrick D. Bolton🇬🇧 · Frank F. Deppisch🇬🇧 · Lukáš Gráf🇩🇪 · Fedor Šimkovic🇸🇰

    Usually considered a background for experimental searches for the hypothetical neutrinoless double beta decay process, two-neutrino double beta decay nevertheless provides a complementary probe of physics beyond the Standard Model. In this paper we investigate how the presence of a sterile neutrino, coupled to the Standard Model either via a left-handed or right-handed current, affects the energy distribution and angular correlation of the outgoing electrons in two-neutrino double beta decay. We pay particular attention on the behaviour of the energy distribution at the kinematic endpoint and we estimate the current limits on the active-sterile mixing and effective right-handed coupling using current experimental data as a function of the sterile neutrino mass. We also investigate the sensitivities of future experiments. Our results complement the corresponding constraints on sterile neutrinos from single beta decay measurements in the 0.1 - 10 MeV mass range.

    hep-phhep-exnucl-exPRD(2021)·49 citations
12. 12*

    Single Transverse-Spin Asymmetry and Sivers Function in Large Momentum Effective Theory

    Xiangdong Ji🇺🇸 · Yizhuang Liu🇨🇳 · Andreas Schäfer🇩🇪 · Feng Yuan🇺🇸

    We apply recent developments in large momentum effective theory (LaMET) to formulate a non-perturbative calculation of the single-transverse spin asymmetry in terms of the quasi transverse-momentum-dependent quark distribution functions from the so-called Sivers mechanism. When the spin asymmetry is defined as the ratio of the quark Sivers function over the spin averaged distribution, it can be directly calculated in terms of the relevant quasi distributions with the soft functions and perturbative matching kernels cancelling out. Apart from the general formula presented, we have verified the result in the small transverse distance limit at one-loop order, which reduces to a collinear expansion at twist-three level.

    hep-phhep-exhep-latnucl-thPRD(2021)·29 citations
13. 13*

    Bottomonium production and polarization in the NRQCD with $k_T$-factorization. III: ${\rm Y}(1S)$ and ${\chi }_b(1P)$ mesons

    N.A. Abdulov🇷🇺 · A.V. Lipatov🇷🇺

    The ${\rm Y}(1S)$ meson production and polarization at high energies is studied in the framework of the $k_T$-factorization approach. Our consideration is based on the non-relativistic QCD formalism for a bound states formation and off-shell production amplitudes for hard partonic subprocesses. The direct production mechanism, feed-down contributions from radiative ${\chi }_b(mP)$ decays and contributions from ${\rm Y}(3S)$ and ${\rm Y}(2S)$ decays are taken into account. The transverse momentum dependent (TMD) gluon densities in a proton were derived from the Ciafaloni-Catani-Fiorani-Marchesini evolution equation and the Kimber-Martin-Ryskin prescription. Treating the non-perturbative color octet transitions in terms of multipole radiation theory, we extract the corresponding non-perturbative matrix elements for ${\rm Y}(1S)$ and ${\chi }_b(1P)$ mesons from a combined fit to transverse momenta distributions measured at various LHC experiments. Then we apply the extracted values to investigate the polarization parameters ${\lambda }_{\theta }$, ${\lambda }_{\varphi }$ and ${\lambda }_{\theta \varphi }$, which determine the ${\rm Y}(1S)$ spin density matrix. Our predictions have a reasonably good agreement with the currently available Tevatron and LHC data within the theoretical and experimental uncertainties.

    hep-phEPJC(2021)·6 citations
14. 14*

    Chiral separation effect for spin 3/2 fermions

    Z.V.Khaidukov🇷🇺 · R.A.Abramchuk🇷🇺

    Chiral Separation Effect (CSE) for systems that feature spin 3/2 fermions was considered. For the self-consistent Adler's model with relativistic massless Rarita-Schwinger fermions (RSA model), we found that the CSE conductivity is five times larger than for massless Dirac fermions. For a model of four-fold band crossing in Rarita-Schwinger-Weyl semimetals, in which massless fermions with quasispin 3/2 exist, we calculated that the CSE conductivity is four times larger than for Weyl fermions. We show that CSE conductivity for any multi-degenerate Fermi point in topological semimetals is proportional to its Chern number and is topologically protected. Along the calculations, we proved an index theorem that relates Chern number of a Fermi-point and spectral asymmetry of the corresponding Landau band structure. The assumption that CSE for any system of chiral fermions is dictated by the corresponding Chern number is found to be correct for RSA model (and for the Dirac fermions).

    hep-phJHEP(2021)·3 citations
15. 15*

    The $Z_{cs}(3985)$ as a threshold effect from the ${\bar{D}}_s^{\ast }D+{\bar{D}}_s{D}^{\ast }$ interaction

    Natsumi Ikeno🇯🇵 · Raquel Molina🇪🇸 · Eulogio Oset🇪🇸

    We study the $e^{+}{e}^{-}\to K^{+}(D_s^{\ast -}{D}^0+D_s^{-}{D}^{\ast 0})$ reaction recently measured at BESIII, from where a new $Z_{cs}$ state has been reported. We study the interaction of ${\bar{D}}_s{D}^{\ast }$ with the coupled channels $J/\psi K^{-}$, $K^{\ast -}{\eta }_c$, $D_s^{-}{D}^{\ast 0}$, $D_s^{\ast -}{D}^0$ by means of an extension to the charm sector of the local hidden gauge approach. We find that the $D_s^{-}{D}^{\ast 0}+D_s^{\ast -}{D}^0$ combination couples to $J/\psi K^{-}$ and $K^{\ast -}{\eta }_c$, but the $D_s^{-}{D}^{\ast 0}-D_s^{\ast -}{D}^0$ combination does not. The coupled channels help to build up strength in the $D_s^{-}{D}^{\ast 0}+D_s^{\ast -}{D}^0$ diagonal scattering matrix close to threshold and, although the interaction is not strong enough to produce a bound state or resonance, it is sufficient to produce a large accumulation of strength at the ${\bar{D}}_s{D}^{\ast }$ threshold in the $e^{+}{e}^{-}\to K^{+}(D_s^{\ast -}{D}^0+D_s^{-}{D}^{\ast 0})$ reaction in agreement with experiment.

    hep-phhep-exPLB(2021)·46 citations
16. 16*

    The Power Spectrum of Density Perturbations in Chain Inflation

    Martin Wolfgang Winkler🇸🇪 · Katherine Freese🇺🇸

    Chain Inflation is an alternative to slow roll inflation in which the universe undergoes a series of transitions between different vacua. The density perturbations (studied in this paper) are seeded by the probabilistic nature of tunneling rather than quantum fluctuations of the inflaton. We find the scalar power spectrum of chain inflation and show that it is fully consistent with a $\Lambda$CDM cosmology. In agreement with some of the previous literature (and disagreement with others), we show that $10^4$ phase transitions per e-fold are required in order to agree with the amplitude of Cosmic Microwave Background anisotropies within the observed range of scales. Interestingly, the amplitude of perturbations constrains chain inflation to a regime of highly unstable de Sitter spaces, which may be favorable from a quantum gravity perspective since the Swampland Conjecture on Trans-Planckian Censorship is automatically satisfied. We provide new analytic estimates for the bounce action and the tunneling rate in periodic potentials which replace the thin-wall approximation in the regime of fast tunneling. Finally, we study model implications and derive an upper limit of $\sim 10^{10}$ GeV on the axion decay constant in viable chain inflation with axions.

    ↳ hep-thastro-ph.COhep-phPRD(2021)·10 citations
17. 17*

    Quantum Correlations in Neutrino Oscillation: Coherence and Entanglement

    M. M. Ettefaghi🇮🇷 · Z. S. Tabatabaei Lotfi🇮🇷 · R. Ramezani Arani🇮🇷

    In this paper, we consider the quantum correlations, coherence and entanglement, in neutrino oscillation. We find that the $l_1$-norm as a coherence measure is equal to sum of the three possible concurrences for measuring the entanglement among different flavor modes which were calculated in the paper by (M. Blasone et al., Europhys. Lett., {\bf 112}, 20007). Our result shows that the origin of the flavor entanglement in neutrino oscillation is the same as that of quantum coherence. Furthermore, in the wave packet framework, the variation of $l_1$-norm is investigated by varying the wave packet width ${\sigma }_x$. As it is expected the amount of coherence increases by ${\sigma }_x$ due to the increase in the overlapping of the mass eigenstates.

    ↳ quant-phhep-phEPL(2020)·18 citations
18. 18*

    Meson spectrum in the large $N$ limit

    Margarita García Pérez🇪🇸 · Antonio González-Arroyo🇪🇸 · Masanori Okawa🇯🇵

    We present the result of our computation of the lowest lying meson masses for SU(N) gauge theory in the large $N$ limit (with $N_f/N⟶0$). The final values are given in units of the square root of the string tension, and with errors which account for both statistical and systematic errors. By using 4 different values of the lattice spacing we have seen that our results scale properly. We have studied various values of $N$ (169, 289 and 361) to monitor the N-dependence of the most sensitive quantities. Our methodology is based upon a first principles approach (lattice gauge theory) combined with large $N$ volume independence. We employed both Wilson fermions and twisted mass fermions with maximal twist. In addition to masses in the pseudoscalar, vector, scalar and axial vector channels, we also give results on the pseudoscalar decay constant and various remormalization factors.

    ↳ hep-lathep-phhep-thJHEP(2021)·36 citations
19. 19*

    Static force potential of non-abelian gauge theory at a finite box in Coulomb gauge

    Tomohiro Furukawa🇯🇵 · Keiichi Ishibashi🇯🇵 · H. Itoyama🇯🇵 · Satoshi Kambayashi🇯🇵

    Force potential exerting between two classical static sources of pure non-abelian gauge theory in the Coulomb gauge is reconsidered at a periodic/twisted box of size $L^3$. Its perturbative behavior is examined by the short-distance expansion as well as by the derivative expansion. The latter expansion to one-loop order confirms the well-known change in the effective coupling constant at the Coulomb part as well as the Uehling potential while the former is given by the convolution of two Coulomb Green functions being non-singular at $\mathbf{x}=\mathbf{y}$. The effect of the twist comes in through its Green function of the sector.

    ↳ hep-thhep-phPRD(2021)·0 citations
20. 20*

    Formation of inflaton halos after inflation

    Benedikt Eggemeier🇩🇪 · Jens C. Niemeyer🇩🇪 · Richard Easther🇳🇿

    The early Universe may have passed through an extended period of matter-dominated expansion following inflation and prior to the onset of radiation domination. Sub-horizon density perturbations grow gravitationally during such an epoch, collapsing into bound structures if it lasts long enough. The strong analogy between this phase and structure formation in the present-day universe allows the use of N-body simulations and approximate methods for halo formation to model the fragmentation of the inflaton condensate into inflaton halos. For a simple model we find these halos have masses of up to $20\mathrm{kg}$ and radii of the order of $10^{-20}\mathrm{m}$, roughly $10^{-24}$ seconds after the Big Bang. We find that the N-body halo mass function matches predictions of the mass-Peak Patch method and the Press-Schechter formalism within the expected range of scales. A long matter-dominated phase would imply that reheating and thermalization occurs in a universe with large variations in density, potentially modifying the dynamics of this process. In addition, large overdensities can source gravitational waves and may lead to the formation of primordial black holes.

    ↳ astro-ph.COhep-phhep-thPRD(2021)·36 citations
21. 21*

    Nucleon axial and pseudoscalar form factors from lattice QCD at the physical point

    C. Alexandrou (Univ. of Cyprus and The Cyprus Inst.)🇨🇾 · S. Bacchio (The Cyprus Inst.)🇨🇾 · M. Constantinou (Temple Univ.)🇺🇸 · P. Dimopoulos (Univ. of Parma and INFN)🇮🇹 · J. Finkenrath (The Cyprus Inst.)🇨🇾 · K. Hadjiyiannakou (Univ. of Cyprus and The Cyprus Inst.)🇨🇾 · K. Jansen (DESY-Zeuthen)🇩🇪 · G. Koutsou (The Cyprus Inst.)🇨🇾 · B. Kostrzewa (Univ. of Bonn)🇩🇪 · T. Leontiou (Frederick Univ.)🇨🇾 · C. Urbach (Univ. of Bonn)🇩🇪

    We compute the nucleon axial and induced pseudoscalar form factors using three ensembles of gauge configurations, generated with dynamical light quarks with mass tuned to approximately their physical value. One of the ensembles also includes the strange and charm quarks with their mass close to physical. The latter ensemble has large statistics and finer lattice spacing and it is used to obtain final results, while the other two are used for assessing volume effects. The pseudoscalar form factor is also computed using these ensembles. We examine the momentum dependence of these form factors as well as relations based on pion pole dominance and the partially conserved axial-vector current hypothesis.

    ↳ hep-lathep-phnucl-exnucl-thPRD(2021)·87 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.